Oligomeric oxolanyl compounds have been utilized as microstructure (1,2-vinyl content) modifiers in the preparation of (co)polymers having a 1,2-microstructure of between 10 and 95 percent from a monomer system which contains at least one conjugated diene monomer. Certain of these oxolanyl compounds have at least two chiral centers that result in the existence of D, L and meso sterioisomers. Commercially available compositions of oxolanyl compounds such as 2,2-di(2-tetrahydrofuryl)propane contain a mixture of approximately 50% D, L isomers and approximately 50% of the meso isomer.